Combining GTOs (Gate Turn-Off thyristor) with MOSFETs yields new devices, including IGCTs (Integrated Gate Commutated Thyristors) and ETOs (Emitter Turn-Off thyristors). While these devices promise very high switching powers, they are relatively slow and exhibit high switching and conduction losses.
FIGS. 1 and 2 show diagrams of an IGCT and an ETO. The measurements shown in the original data of FIG. 3 demonstrate how the critical turn-off times decrease with decreasing temperature of a IGCT thyristor switch [Ref. 2]. It was earlier known that GTOs provide similar improved performance at reduced temperatures. Turn-on and delay times (not shown) are also improved. Many additional measurements on IGCTs and MTOs (MOSFETs in gate turn-off circuitry) are presented in reference 2, which is an unpublished report prepared by the inventors. These FIG. 3 curves demonstrate how decreasing the operating junction temperature improves performance.
The measurements in FIG. 3 were made cooling only the power device, the basic thyristor switch GTO. The driver circuitry was not designed for operation at cryogenic temperatures, and so was not cooled.